[drevan]

I got the SES light the other day and when i ran the codes trough my OBDII scanner i got P3026 & P0135 (B1S1).

I read mixed comments that S1s are PITA to get to, but others say that B1 its easer to change. I am wondering is the procedure the same to replace B1 and B2 sensors if so ill do them both while there?

[kkasson]

Originally Posted by drevan

I got the SES light the other day and when i ran the codes trough my OBDII scanner i got P3026 & P0135 (B1S1).

I read mixed comments that S1s are PITA to get to, but others say that B1 its easer to change. I am wondering is the procedure the same to replace B1 and B2 sensors if so ill do them both while there?

B1 is Bank 1, i.e. cylinders 1-3 and B2 is cylinders 4-6. S1 is the pre-cat sensor. It's right next to the valve cover on the exhaust side, just look at the top of the engine and you'll see it. One of them might have a little less room to get to it, but they're both right there. The post-cat (S2) sensors are underneath the car.

[mweisdorfer]

http://www.e90post.com/forums/showth...=oxygen+sensor

Scroll halfway down and there is a DIY video.

I would change them in pairs; I would not think its necessary to change all 4 of them out, but you certainly should change out the matching pre-cat or post-cat o2 sensor even though you may not be getting a code on that specific one. So, if one pre-cat is bad, then change out the other pre-cat even though its ok.

This is for the 335.

[drevan]

Thanks, i wasn't going to touch S2 (post cat) sensors, i was debating if i should change both or just the bad pre cat sensor. Ill take my chances and change just the bad one.